The Intex spa tubs have a pressure release valve at the bottom of the outer wall. It works as shown below:
The pressure release valve is located at the bottom of the outer wall.
For example: The spa is inflated in the morning.
Through exposure to the sun and warm weather, the air expands and the pressure increases. The pressure relief valve allows the excess pressure to escape.
At night and at lower temperatures, the air automatically contracts, which makes the spa tub seem less sturdy. The spa tub is not leaking!
The pressure will recover when the air temperature rises again. If the temperature is low, you can re-fill the air if necessary.
If the problem has not been resolved, it is possible that the problem is in the pressure release valve. Please read Checking pressure release valve or contact local service centre for further assistance.